This invention relates to a method for making an animal feed supplement and, in particular, a molasses-based animal feed supplement in solid, block form.
The value of molasses-containing supplements as a palatable carbohydrate source and nutrient vehicle in animal diets has been recognized for many years. Phosphoric acid has often been added to the molasses supplement to serve as an acidic preservative and as a source of dietary phosphorus. Urea has been added to animal feed supplements to supply non-protein nitrogen, and fats and vitamins have also been included as ingredients in animal feed supplements. Molasses-based feed supplements are particularly valuable fed either "free-choice" to grazing cattle or to stock in confinement where feed mixing facilities are lacking. (Free-choice feeding allows the animal to consume from a conveniently placed reservoir of liquid or solid supplement according to need.) Consumption during free-choice feeding is controlled by use of a lick wheel with liquids or by varying the hardness of a feed block, both means limiting the animal's ease of feeding. Controlling palatability of the feed block by chemical means also limits consumption.
Solid animal feed supplements have been prepared from molasses and other ingredients to augment the dietary requirements of animals, especially cattle, when forage is scarce or of low quality, for example, during the summer months in California and summer through winter in the Pacific Northwest. Solid feed blocks offer the advantage of free choice feeding of cattle, thereby reducing the labor and expense otherwise incurred to mix the feed supplement with the cattle's feed ration. Molasses blocks have been manufactured by compressing ingredients into a molded shape or by evaporative heating of the ingredients. Both of these methods have certain disadvantages. For example, energy-supplying ingredients, such as molasses, and heat-sensitive vitamins (if added) many degrade during heating to the temperature necessary to evaporate water.
Additional dietary requirements develop during the seasonal periods when grasses are growing rapidly, usually in the spring of the year. During these periods, the magnesium content of grazing grasses is so low that a condition of hypomagnesemia, commonly known as "grass tetany," often develops in grazing herds. The condition manifests itself in the animal staggering or going into convulsions, and hypomagnesemia can even cause death in severe cases. The situation is worsened if a high nitrogen or potassium-content fertilizer is applied to the grassland to encourage plant growth since uptake of magnesium from the soil is thereby depressed.
To counteract the nutritional effects upon grazing herds of grasses with low magnesium content, animal feed supplements in the form of a liquid or a solid block containing molasses and a concentration of magnesium additive sufficient to overcome dietary deficiencies of the nutrient have been provided. Animal feed blocks containing molasses and magnesium as a nutritional supplement have been disclosed in U.S. Pat. No. 4,234,608 to Linehan wherein magnesium oxide and dicalcium phosphate are reacted in molasses-containing solution to form a solid feed block. U.S. Pat. Nos. 4,171,385, 4,171,386 and 4,265,916 to Skoch, et al. also incorporate magnesium oxide as a nutritional source with or without the use of ferrous sulfate as an additional blocking agent to form a moldable mixture. However, magnesium oxide is highly alkaline and only sparingly soluble in molasses so that mixing of solutions containing magnesium oxide to maintain uniform dispersion requires great expenditures of energy. Moreover, magnesium oxide, because of its sparing solubility in molasses solutions, reacts slowly with phosphate so that gelation requires at least one hour and more commonly several hours.
As magnesium oxide is a highly basic substance, the animal feed supplements incorporating it as a source of magnesium ions are usually highly basic, having a pH in the range from about 9.5 to 11 pH units. A particular disadvantage of alkaline animal feed supplements containing nitrogen sources, such as urea, is that grazing animals tend to produce free ammonia from such feed during rumination. In a high pH environment, sufficient free ammonia can be produced from the nitrogen source in the rumen of the animal to cause ammonia poisoning leading to death.
In U.S. Pat. No. 4,027,043, animal feed supplements are disclosed which are prepared by mixing a phosphate source and an aluminum or an alkaline earth metal ingredient with molasses to solidify the resultant mixture at an acidic pH. This patent discloses that the combination of a soluble phosphate or phosphoric acid, at from 0.5 to 5 weight percent P.sub.2 O.sub.5, and an oxide or salt of aluminum, magnesium, calcium or mixture thereof, at from 0.5 to about 5 weight percent (expressed as the oxide) will solidify molasses.
The use of calcium chloride in liquid molasses-based supplements for cattle and its effect upon solidification has been investigated by Grosso and Nelson. (See "Calcium Chloride in Liquid Feed Supplements" reported in complete texts of the speeches given at the 1973 annual convention, NFIA-COUNTER '73, Oct. 14-16, 1973, Louisville, KY.) The object of these investigators was to provide liquid supplements with high soluble calcium content and avoid solidification; nevertheless, some of the formulations they prepared did solidify. The formulations that did solidify generally did not have a nutritionally appropriate amount of phosphorus, that is, they contained either too much or too little phosphorus they contained no magnesium additive. Certain of the other formulations that had nutritionally appropriate amounts of phosphorus did not harden since the phosphorus was supplied as a polyphosphate. (It has been found in the present invention that polyphosphate does not interact with calcium ions at acidic pH to provide a solid product at nutritionally appropriate levels of calcium and phosphorus concentrations, or at convenient temperature and mixing conditions. In addition, when soluble salts of magnesium are introduced into molasses feed supplements at nutritional levels, the mixture will not gel at acidic pH to satisfactory hardness.)
One major problem in the making of animal feed blocks results from the desire to transport and store the feed supplement as a liquid, so that solid blocks can be made from the liquid at remote locations and/or in small lots as the need arises. Sometimes it is more convenient to transport liquid solutions of molasses-containing feed supplements to remote blocking sites for storage than to transport and store molasses blocks. If the blocks can be rapidly and easily solidified on demand from liquid at remote sites, blocks can be manufactured from the liquid solution at will on site to meet the immediate nutritional requirements of the herd by incorporating extra vitamins, medicaments, and the like. However, to accomplish this goal, the nutritional and blocking agents added to molasses, especially the phosphorus, magnesium and calcium, must be substantially soluble in molasses or aqueous solutions. Molasses solutions prepared with less soluble ingredients, such as magnesium oxide, rapidly separate upon standing with the result that the solutions require constant stirring with power mixers before molasses blocks can be made. Therefore, when it is more convenient to manufacture blocks from stored solutions as needed or to meet the varying needs of the herd for vitamins, and the like, it is desirable to have a method of rapidly and easily preparing such solid feed blocks from substantially homogeneous liquid solutions that gel rapidly.
In addition, it is also desirable to have a method for preparing acidic solid, molasses-based animal feed supplements having nutritionally beneficial contents of phosphorus, magnesium and nitrogen which solidify rapidly when the ingredients are mixed at convenient temperature and which do not subject grazing herds to ammonia poisoning, but do counter the effects of hypomagnesemia during seasons of rapidly growing grasses.